Now I have changed my previous design that used hammer valve and this new design uses GEV as valve.The number 1 is main reservoir that holds in about 8bar and then regulator regulates it to 4bar(number 2).The main reservoir volume is about 2liters 8bars of air pressure that is 16liters of normal air pressure and the second chamber volume is 100mland pressure 4bar that makes 400ml of normal air pressure,so if I calculate fast,I cand shoot ten times and after it the main reservoir pressure is still ,10x0.4liters=4liters of normal pressure, and pressure is then in main reservoir 16-4=12liters/2=6bar.What do you think?You get it?

This is the formula I use to figure stuff like this out. Just replace your inputs (you may want to convert them first, as this is not using metric measurements) and it will assist you in determining the amount of times your main reservoir will fill the smaller reservoir.

But, yeah, get the bugs worked out, if any, and get a fast regulator, and have a semi-auto marble gun.

(Or you could just hook directly to the compressor / air tank and bypass the main chamber).